Weathering plastic or wood to make it look like aged metal is an effect you can achieve in less steps than most people expect. The *most* basic weathering can be done with only two paints. Here, I’ll show you how to weather and age using only three paints. This technique is how I weathered, in less than 10 minutes, a 3D-printed robot we made here at the MAKE offices.

Step #1: Pick a basecoat.

The white piece shown here is actually from the back of the robot. It was 3D-printed here at the MAKE office.

I painted the robot bright red, to mimic our Maker Faire robot mascot. I choose Krylon's Fusion brand, with the right red I was looking for. It dries pretty quickly and adheres to plastic really well. I skipped the priming process, but you can put this paint over primer easily enough.

Step #2: Pick a metallic paint for worn edges.

Step #3: Start drybrushing over the piece.

You need the right type of brush to get the right drybrushing results. Take an old brush that has a lot of bristles and cut the end off so it's flat. Or buy a specific brush that's already made for drybrushing, like MicroMark's Dry Brushes (shown here).

Dab the brush into the paint, and then take the brush and remove most of the paint onto a paper towel. Drybrushing means exactly that: the brush should not be wet with paint, it needs to have barely any paint on it. Practice on something other than your model to get the hang of it.
Drybrushing correctly will leave just a little paint on the raised edges of your piece. Remember to keep a light hand and go slowly.

For machined edges, I focus on adding a bit more paint around the main edges of a model. Imagine that those edges are what other objects come into contact with the most, and therefore, need to look more worn.

Step #5: Add dirt and grunge easily.

Let's start adding some dirt and grime to make this look dirty. We'll start by making a wash. A wash is pretty simple, watered-down acrylic black paint. If you brush over newspaper and can still read the print, it's probably watered down enough.
Another pro tip: don't buy wash mediums at the art store. Instead, just windshield washer fluid to thin acrylic paints. It dries quickly and will last you years.

I generously apply the paint in all the nooks and crannies that dirt would normally gather in. If the paint is watery enough, it should run into all the valleys of your model quickly.

Depending on how much of this effect you want, you can dab up the paint immediately, leaving only a little black grime, or paint generously over the model and leave the paint on to dry for a more dramatic effect.

Step #6: That's it!

It's pretty easy to get basic weathering effects, as you can see. There are more degrees of weathering you can expand upon: pigments, rusting agents, and other cool techniques are out there to find and invent!